Furnace for smelting the residues from evaporated waste cellulose lyes



HZ 1933. H. N. UNDEN 1,910,724

FURNACE FOR SMELTING THE RESIDUES FROM EVAPO RATED' WASTE CELLULOSE LYES Filed March 6, 1950 l 'atentecl May 23, 1933 @TATES PATENT OFFEGE- HANS NIKLAS UNDEN, OF NENSJ'O, SWEDEN FURNACE FOR SMELTING THE RESIDUES FROM EVAPCRATED WASTE GELLULOSE LYES Application filed March 6, 1930, Serial No.

In manufacturing cellulose according to alkaline methods such as sulphate method, soda method etc., the regeneration of the Waste lye is of the greatest economical importance. This regeneration is principally executed in such a manner, that the waste lye, the so-called black lye, is evaporated in suitableevaporating apparatus, where a dry product is obtained. This product is burnt in special smelting furnaces, into which air under pressure is introduced. The heat generated on burning the organic constituents is suflicient for smelting the inorganic salts consisting principally of soda,

which flows out from the furnace in a molten condition.

The air required for this combustion is supplied througl'i a tuycre, which is cooled by means of circulating water, air or other cooling medium.

The upper end of the tuyere is connected with a fan-blower or other high pressure blower, While the lower end of the same is located within the smelting furnace.

In the old types of furnaces the tuyeres in the form of hollow cylinders were fully open at the lower end, due to which fact a thick air current was introduced into the furnaces. In such furnaces the tuyeres were either vertical or horizontal. The horizontal arrange ment of the tuyeres has, however, been very little used due to the risks occurring in its employment.

In recent years a proposal has been made 3 to make the vertical tuyeres closed at their bottoms and to arrange two diametrically located wide openings at the lower end of the mantle surface, so that two thick air currents are directed to both sides.

In both types of such tuyeres a relatively low air pressure has been used, about 50 to 100 millimeters of water column. This is due to the fact, that the voluminous air current or currents has a very unfavorable action on the lining of the furnace chamber. This unfavorable action results in this, after a short time in the formation of a cavity in the bottom below the outlet opening of the tuyere or in the side walls in front of the diametrically opposed wide side openings.

433,708, and in Sweden October 22, 1929.

These defects necessitate repairs and cause interruptions in the work.

Another inconvenience by using such a voluminous air current consists in the fact that the excess of air introduced into the furnace chamber, will become too great, which causes a higher loss of chemicals, because the sodium sulphate, added for compensating the loss of alkali in the sulphate method, is

sublimatedand the powder escapes with the 0 air current out of the furnace and deposits itself for instance on the tubes of a steam boiler, thus preventing the transmission of heat, or said powder may escape through the chimney.

A further inconvenience caused by using such voluminous air currents consists in this, that the combustion is concentrated to the bottom or the side walls in front of the wide openings in the tuyre. This causes a rapid 0 consumption of the solid mass in the vicinity of the opening or openings, and round this or these places hard deposits are formed preventing fresh quantities of mass to come down and be acted upon by the air current. Said deposits must therefore be removed by iron bars before fresh mass can be supplied.

Due to these inconveniences the work of said smelting furnaces has hitherto been highly intermittent and caused a great deal of work and surveying.

Applicants invention has for its object a method, by which these inconveniences are avoided. This is accomplished by exposing the air to a very high pressure, for instance at least 200 millimeters of water column, and by causing the same to escape through a plurality of relatively small openings in all directions from the lower part of the tuyere. The pressure should be so adapted, that each narrow air current enters to a certain depth into the surrounding mass but not so far, that the air currents will come into contact with the bottom or the side walls of the furnace chamber. By choosing a suitable diameter of the outlet openings for the air and a suitable pressure of the air, a very hot zone is formed around the lower end of the tuyere, which zone is surrounded by a colder zone of mass forming a protection for the bottom and the walls of the furnace chamber, where fore these will be very tenable and not so often necessitate repairs.

Another advantage, due to the fact that one part of the air currents are directed upwards, consists in a preheating of, and a reacting in the mass in the upper part of the furnace chamber wherefore said mass slowly sinks down, no deposits being formed, and consequently no removing of such deposits with interruptions of the work are necessary. The work of the furnace will therefore be fully continuous, and the intensity of the same may be regulated within wide limits by varying the pressure of the air. Moreover, it has been found, that, in contradistinction to the case in the previously used tuyeres, no eXcess of air is found in the furnace chamber but more frequently a lack of air, as it is necessary to supply secondary air for the combustion of the gases. This offers the advantage, that the arch of the furnace and the brickwork in the gas-channels going to the above situated combustion furnace are protected, as the secondary air is supplied only into the last-mentioned furnace.

A practical form of embodiment is illustrated on the accompanying drawing, which shows a vertical section through a smelting furnace with a tuyre arranged according to the present invention introduced into the same.

1 designates the brickwork of the smelting furnace, 2 its inclined bottom and 3 the outlet opening for the molten mass. In the arch 4 there is an opening 5, through which the tuyere 6 is introduced. The tuyere shown on the drawing is adapted to be cooled with water, the water being led through conduit 7 is introduced into the space between the double-walls of the tuyere. Air coming from a fan-blower, not shown, is introduced at 8.

The lower end 9 of the tuyere is enlarged so as to form a substantially globe-shaped enlargement, which is provided with a great number of relatively narrow channels 10, which extend in all directions, consequently to the sides as well as obliquely upwards and downwards. The enlargement 9 may of course also have another form than the form of a globe, providingthat is possible to arrange the air channels in such a way, that they are directed to all sides. The globeshape, however, is the most convenient one, as it prevents the mass from sticking to its upper parts on moving downwards.

I claim:

Tuyere for furnaces for smelting residues from evaporated black liquor from sulphate or sodium cellulose factories, comprising a double walled tubular body, means for introducing cooling water into the space between said double walls, means for introducing air under pressure into the tuyere, a hollow, bulb-shaped enlargement at the lower end of the tuyere, said bulb-shaped enlargement being also double walled and adapted to be cooled by the water, and narrow channels leading in all directions from the interior of the bulb to its outside, through which the air is led out in all directions from the bulb.

In testimony whereof I have hereunto affixed my signature.

HANS NIKLAS UNDEN, 

